In the related art, a photolithography technology has been widely used to fabricate a fine pattern to manufacture a large-scale integration (LSI) circuit. However, the photolithography technology has a problem in that it is difficult to fabricate a pattern having a size smaller than a wavelength of the light used in exposure. In addition, as another fine pattern fabrication technology, there is known a mask pattern lithography technology (EB method) using an electron beam lithography system. However, in the EB method, a lithograph time increases as the number of lithograph patterns increases because of directly forming a mask pattern by lithography using electron beams, and a throughput until pattern formation significantly decreases. In addition, a problem also occurs in that costs of apparatuses increase in such methods due to high-precision control for a mask position in a photolithography exposure apparatus or a large size of the electron beam lithography system in the EB exposure apparatus.
As a fine pattern fabrication technology capable of addressing such problems, there is known a nanoimprint lithography technology. In the nanoimprint lithography technology, a fine pattern formed on a mold is transferred onto a surface of a transfer target substrate by pressing the mold having a fine pattern of nanoscale to a resist film formed on a surface of the transfer target substrate.
FIGS. 1A and 1B are explanatory diagrams illustrating an exemplary nanoimprint lithography method. Referring to FIG. 1A, in order to form a concavo-convex structure on a surface of a desired substrate (object to be processed) 1001, a fine pattern 1003 formed on a mold 1002 is pressed to the object 1001 to be processed by applying a nanoimprint lithography method.
In a case where a fine pattern 1003 is used as a mask for fabricating the object 1001 to be processed, the fine pattern 1003 is made of a transfer material serving as a mask when the object 1001 to be processed is fabricated. When the transfer is performed, it is necessary to reduce a remaining film thickness T. In order to reduce the remaining film thickness T, it is necessary to reduce a thickness of the coating of the transfer material and press it with a high pressure for a long time and the likes. However, as the thickness of the coating is reduced, the object 1001 to be processed becomes susceptible to roughness or particles existing on a surface of the object 1001 to be processed, and moreover a transfer material may be unsatisfactorily filled in the concavo-convex structure of the mold 1002, or vapors may be incorporated. If pressing is made for a long time, throughput reliability is degraded. In addition, in order to uniformly form the thin remaining film, it is also necessary to use a special apparatus having a minute pressure distribution. Particularly, it is known that it is very difficult to form a homogeneous thin remaining film in a large scale. For these problems, it is difficult to take overall advantages such as transferability in a large scale, convenience, or throughput reliability of the nanoimprint lithography considered to be industrially superior.
Meanwhile, in a case where a fine pattern having a high aspect ratio is formed on the object 1001 to be processed, it is necessary to increase an aspect ratio of the fine pattern formed on a surface of the mold 1002. However, as the aspect ratio of the fine pattern formed on a surface of the mold 1002 increases, a filling error may be easily generated, and a demolding error such as a breakdown of the fine pattern 1003 may be easily generated when the mold 1002 is removed. As illustrated in FIG. 1B, in order to form the fine pattern 1003 having a high aspect ratio on the object 1001 to be processed, a method has been proposed, in which an organic layer 1004 (mask layer) is provided on the object 1001 to be processed, a fine pattern 1003 is formed on the organic layer 1004, and the organic layer 1004 is fabricated by using the fine pattern 1003 as a mask. However, even when the fine pattern 1003 is used as a mask for fabricating the organic layer 1004, the aforementioned problems still exist.
Among them, a method of forming a fine mask pattern having a thin or no remaining film T has been proposed (refer to Japanese Unexamined Patent Application No. 2011-66273). In Japanese Unexamined Patent Application No. 2011-66273, first, a mask material film is directly formed on a concavo-convex structure having unevenness on a surface. Subsequently, the remaining film T is thinned or has a zero thickness by performing etch-back for the mask material film (a thickness of the mask material film arranged on the concavo-convex structure of the mold is thinned). Then, a substrate is laminated to the mask material, and, finally, ashing is performed for the mold side, so that a fine mask pattern having no remaining film T excluding a fine structure in the mold is obtained.